Vehicles, such as cars, are usually equipped with airbag devices that inflate and deploy airbags in the vehicle to absorb impact applied to occupants in an emergency, such as a collision or an abrupt slowdown. Various types of airbag devices have been developed and employed, including driver's seat airbag devices installed in steering wheels, passenger airbag devices installed in instrument panels, side airbag devices installed in side surfaces or seats of vehicles, curtain airbag devices installed in upper parts of doors, knee airbag devices for protecting occupants' knees, and pedestrian airbag devices installed under hoods.
Such an airbag device usually includes an airbag that is normally folded and is inflated and deployed in an emergency, an inflator for supplying gas to the airbag, and a retainer for holding the airbag and the inflator. Furthermore, the airbag sometimes has, for example, a strap for restricting the width of the inflated and deployed airbag or a strap for controlling opening and closing of a vent hole. As a strap retention device for releasably retaining the strap (this may also be called a “strap releasing device”), one using a cutter (cutting edge) has already been proposed (for example, see Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2008-543656, Japanese Patent No. 4649508 and Japanese Unexamined Patent Application Publication No. 2008-162584). Note that the strap is a cord or fabric-like member that can apply tension to an object and is sometimes called a tether, an anchor rope, an anchor cable, or the like.
An airbag tether release mechanism disclosed in Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2008-543656 includes a housing having an opening through which a tether can pass, a cutter disposed in the housing, and an initiation device (pyrotechnic device) causing the cutter to slide in the housing. The airbag tether release mechanism is configured such that the tether is allowed to pass through the opening and is retained, and when the initiation device is activated, the cutter slides in the housing at least to a position where it is aligned with the opening and cuts the tether.
An actuator disclosed in Japanese Patent No. 4649508 includes a cylindrical casing having an attachment hole through which a tether can pass, a cutter disposed in the casing, and a gas generator axially driving the cutter in the casing. The actuator is configured such that the tether is allowed pass through the attachment hole and is retained, and when the gas generator is activated, the cutter axially moves in the casing and cuts the tether by a shearing force generated as it crosses the attachment hole.
A tether retention system disclosed in Japanese Unexamined Patent Application Publication No. 2008-162584 includes a tether holder attached to a tether, a housing having a hole through which the tether holder can pass, a cutter disposed in the housing, and an initiator causing the cutter to slide in the housing. The tether retention system is configured such that the tether holder is allowed to pass through the hole and is retained, and when the initiator is activated, the cutter slides in the housing, passes through the hole, and cuts the tether.